An end mill is used for slot milling or side cutting a workpiece, and the like. For example, Patent Document 1 describes a four-flute end mill that includes, as end cutting edges, two long cutting edges (8b, 8d) and two short cutting edges (8a, 8c). The two long cutting edges (8b, 8d) extend from an outer periphery, connect to a chisel portion, and are point symmetrical with a rotational axis serving as the center of symmetry. The two short cutting edges (8a, 8c) are located between the long cutting edges and away from the chisel portion, extending from the outer periphery toward the rotational axis side.
In such an end mill, the cutting resistance during cutting is known to be large at the center of the end mill, that is, near the rotational axis. Here, in Patent Document 1, a gash on a side of the short cutting edge is cut to an area near the rotational axis, thereby forming a chisel portion having a thin thickness at a position between the long cutting edges that includes the rotational axis, and thus decreasing flaws near the rotational axis. According to the end mill in Patent Document 1, the end mill has between the chisel portion and a tip relief face that continues to the chisel portion, a thickness that locally decreases and a thick thickness on both sides of the thickness, and forms a V-shaped bend point, when viewed from a distal end.
Patent Document 2 describes an end mill that has a thickness between the chisel portion and the tip relief face that gradually decreases, and does not form a bend point.